Expandable interbody spacer

ABSTRACT

An expandable interbody spacer for the spine is provided. The interbody spacer includes a housing, upper and lower endplates, an anterior actuator, a posterior actuator, an anterior drive screw, and a posterior drive screw. The anterior and posterior drive screws are independently or simultaneously rotated with respect to each other by a driver to wedge one or more of the anterior and posterior actuators between the endplates moving them into parallel and/or angular expansion.

FIELD OF THE INVENTION

This application relates generally to spinal implants, and inparticular, expandable intervertebral spacers and fusion cages.

BACKGROUND OF THE INVENTION

Back pain can be caused by a variety of factors including but notlimited to the rupture or degeneration of one or more intervertebraldiscs due to degenerative disc disease, spondylolisthesis, deformativedisorders, trauma, tumors and the like. In such cases, pain typicallyresults from compression or irritation of spinal nerve roots arisingfrom reduced spacing between adjacent vertebrae, a damaged disc and ormisalignment of the spine resulting from the injury or degeneration.

Common forms of treating such pain include various types of surgicalprocedures in which a damaged disc may be partially or totally excised.After the disc space is prepared, one or more implants are insertedbetween the adjacent vertebrae in an effort to restore the naturalspacing and alignment between the vertebrae, so as to relieve thecompression, irritation or pressure on the spinal nerve or nerves and,thereby, eliminate or significantly reduce the pain that the patient isexperiencing. Typically, one or more implants are used together withsubstances that encourage bone ingrowth to facilitate fusion betweenadjacent vertebrae and achieve immobilization of adjacent bones.Surgeons insert these intervertebral devices to adjunctively facilitatebone fusion in between and into the contiguous involved vertebrae. Thisfusion creates a new solid bone mass and provides weight bearing supportbetween adjacent vertebral bodies which acts to hold the spinal segmentat an appropriate biomechanically restored height as well as to stopmotion in a segment of the spine and alleviate pain.

In a posterior lumbar interbody fusion (PLIF) surgery, spinal fusion isachieved in the lower back by inserting an implant such as a cage andtypically graft material to encourage bone ingrowth directly into thedisc space between adjacent vertebrae. The surgical approach for PLIF isfrom the back of the patient, posterior to the spinal column. Ananterior lumbar interbody fusion (ALIF) surgical procedure is similar tothe PLIF procedure except that in the ALIF procedure, the disc space isfused by approaching the spine through the abdomen from an anteriorapproach instead of from a posterior approach. Another fusion procedureis called a transforaminal lumbar interbody fusion (TLIF) which involvesa posterior and lateral approach to the disc space. To gain access tothe disc space, the facet joint may be removed whereby access is gainedvia the nerve foramen. In an extreme lateral interbody fusion (XLIF),the disc space is accessed from small incisions on the patient's side.

In the typical procedures described above, the adjacent vertebrae mustbe distracted apart by a substantial amount in order to allow thesurgeon to advance the implant with relatively little resistance alongthe delivery path. Also, the surgeon must typically release the implantat least once as the implant is being delivered along the delivery pathand align and position the implant at the target position ofimplantation, typically in the anterior aspect of the disc space. Ifstatic spacers having a fixed height are employed, the right-sizedspacer is selected from a plurality of spacers. Sometimes the selectedstatic spacer must be interchanged for one of a different height duringthe procedure. Expandable spacers provide several advantages over staticspacers. For example, expandable spacers may be more easily inserted intheir low-profile configuration and then mechanically expanded intotheir high-profile configuration when in the right position. Anotheradvantage of some expandable spacers is that the degree of expansioneasily can be adjusted in-situ according to the specific anatomy of thepatient. Generally, expandable spacers avoid the need to stock multiplesizes, and to remove and replace spacers during the procedure.

There is a need to provide an expandable spacer that is capable ofcustomized expansion given a wide variability in patient anatomy at eachvertebral level that meets the surgeon's demands for providing the beststabilization solutions. Sometimes uniform parallel expansion of thespacer is required. Sometimes only distal or proximal angulation of thespacer is required and sometimes a combination of distal or proximalangulation together with parallel expansion is required. Therefore,there is a need to provide a new and improved expandable interbodyspacer that is versatile in both angulation and parallel expansion, easyto position, deploy from a low-profile to a high-profile configuration,angulate both proximally and distally as well as expand uniformly. Thisinvention, as described in the detailed description, sets forth animproved interbody spacer that meets these needs.

SUMMARY OF THE INVENTION

According to one aspect of the invention, an expandable interbody spacerfor the spine is provided. The expandable interbody spacer includes ahousing having two sides interconnected by a distal endwall and aproximal endwall defining a hollow interior. The distal endwall includesa threaded distal opening and the proximal endwall having a threadedproximal opening. The spacer includes an upper endplate and a lowerendplate each having a posterior end and an anterior end, abone-engaging surface and an interior surface opposite to thebone-engaging surface. The interior surface includes an anterior rampsurface extending at an angle with respect to the interior surface and aposterior ramp surface extending at an angle with respect to theinterior surface. The spacer includes an anterior actuator locatedbetween the interior surfaces of the upper endplate and lower endplatenear the distal end of the spacer. The anterior actuator includes anupper anterior actuator segment and a lower anterior actuator segment.The upper anterior actuator segment has a curved inner surface forcontact with the anterior drive screw and an angled leading surface forcontact with the anterior ramp surface of the upper endplate. The loweranterior actuator segment has a curved inner surface for contact withthe anterior drive screw and an angled leading surface for contact withthe anterior ramp surface of the lower endplate. The spacer includes aposterior actuator located between the interior surfaces of the upperendplate and lower endplate near the proximal end of the spacer. Theposterior actuator includes an upper posterior actuator segment and alower posterior actuator segment. The upper posterior actuator segmenthas a curved inner surface for contact with the posterior drive screwand an angled leading surface for contact with the posterior rampsurface of the upper endplate. The lower posterior actuator segment hasa curved inner surface for contact with the posterior drive screw and anangled leading surface for contact with the posterior ramp surface ofthe lower endplate. The anterior drive screw includes a proximal ballhead connected to a distal threaded shank. The ball head of the anteriordrive screw is located between the curved inner surfaces of the upperand lower anterior actuator segments. The distal threaded shank isthreadingly connected to the threaded distal opening. The anterior drivescrew has an anterior drive bore extending from a proximal opening alonga longitudinal drive axis. The spacer includes a posterior drive screwincluding a proximal threaded shank connected to a distal ball head. Theball head of the posterior drive screw is located between the curvedinner surfaces of the upper and lower posterior actuator segments. Theproximal threaded shank is threadingly connected to the threadedproximal opening. The posterior drive screw has a posterior drive boreextending along the longitudinal drive axis between a proximal openingin the threaded shank and a distal opening in the ball head. Rotation ofthe posterior drive screw in a first direction relative to the proximalend of the spacer around the drive axis translates the posterior drivescrew distally to wedge apart and expand the distance between theposterior ends of the upper and lower endplates. Rotation of theanterior drive screw in the first direction relative to the proximal endof the spacer around the drive axis translates the anterior drive screwproximally to wedge apart the anterior ends of the upper and lowerendplates. Rotation of the posterior drive screw in a second directionrelative to the proximal end of the spacer around the drive axistranslates the posterior drive screw proximally to reduce the distancebetween the posterior ends of the upper and lower endplates. Rotation ofthe anterior drive screw in the second direction relative to theproximal end of the spacer around the drive axis translates the anteriordrive screw distally to reduce the distance between the anterior ends ofthe upper and lower endplates.

According to another aspect of the invention, a driver for an expandableinterbody spacer having a proximal end and a distal end is provided. Thedriver includes a first drive portion having a first length extendingalong a longitudinal axis of the driver. The first drive portion has afirst diameter and a non-circular cross-sectional first shape takenperpendicular to the longitudinal axis extending along the first length.The driver includes a second drive portion having a second lengthextending along the longitudinal axis. The second drive portion has asecond diameter and a non-circular cross-sectional second shape takenperpendicular to the longitudinal axis extending along the secondlength. The driver includes a middle portion located between the firstdrive portion and the second drive portion. The middle portion has amiddle length extending along the longitudinal axis. The middle portionhas a middle diameter and a cross-sectional middle shape takenperpendicular to the longitudinal axis extending along the middlelength. The driver includes a handle located at the proximal end. Thehandle has a handle length extending along the longitudinal axis and ahandle diameter. The first drive portion extends from the distal end ofthe spacer to a distal end of the middle portion. The middle portionextends from a proximal end of the first drive portion to a distal endof the second drive portion. The handle extends from a proximal end ofthe second drive portion to the proximal end of the spacer.

According to another aspect of the invention, a method for an interbodyspacer for the spine is provided. The method includes the step ofproviding an expandable interbody spacer having a longitudinal axis, aproximal end and a distal end. The spacer includes a housing having athreaded proximal opening and a threaded distal opening. The spacerincludes an upper endplate having an anterior end and a posterior end.The upper endplate has an anterior angled surface and a posterior angledsurface. The spacer includes a lower endplate having an anterior end anda posterior end. The lower endplate has an anterior angled surface and aposterior angled surface. The spacer includes an anterior drive screwthreadingly connected to the distal opening. The anterior drive screwincludes an anterior ball head connected to a threaded anterior shaft.The anterior drive screw includes an anterior drive bore having a borediameter and a cross-sectional shape taken perpendicular to andextending along a longitudinal drive axis. The spacer includes ananterior actuator coupled to the anterior drive screw. The anterioractuator includes an upper drive surface for mating with the anteriorangled surface of the upper endplate and a lower drive surface formating with the anterior angled surface of the lower endplate. Thespacer includes a posterior drive screw threadingly connected to theproximal opening. The posterior drive screw includes a posterior ballhead connected to a threaded posterior shaft. The posterior drive screwincludes a posterior drive bore having a bore diameter andcross-sectional shape taken perpendicular to and extending along thedrive axis. The posterior drive bore is coaxially aligned with theanterior drive bore along the drive axis. The spacer includes aposterior actuator coupled to the posterior drive screw. The posterioractuator includes an upper drive surface for mating with the posteriorangled surface of the upper endplate and a lower drive surface formating the posterior angled surface of the lower endplate. The methodincludes the step of providing a driver having a longitudinal axis, aproximal end and a distal end. The driver includes a first drive portionhaving a first length extending along a longitudinal axis of the driver.The first drive portion has a first diameter and a non-circularcross-sectional first shape taken perpendicular to the longitudinal axisextending along the first length. The first shape is sized andconfigured to matingly engage the anterior drive bore and the posteriordrive bore to rotate the anterior drive screw or posterior drive screw.The driver includes a second drive portion having a second lengthextending along the longitudinal axis; the second drive portion having asecond diameter and a non-circular cross-sectional second shape takenperpendicular to the longitudinal axis extending along the secondlength. The second shape is sized and configured to matingly engage theposterior drive bore to rotate the posterior drive screw. The driverincludes a middle portion located between the first drive portion andthe second drive portion. The middle portion has a middle lengthextending along the longitudinal axis. The middle portion has a middlediameter and a cross-sectional middle shape taken perpendicular to thelongitudinal axis extending along the middle length. The driver includesa handle located at the proximal end. The handle has a handle lengthextending along the longitudinal axis and a handle diameter. The firstdrive portion extends from the distal end of the spacer to a distal endof the middle portion. The middle portion extends from a proximal end ofthe first drive portion to a distal end of the second drive portion. Thehandle extends from a proximal end of the second drive portion to theproximal end of the driver.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front top perspective view of an expandable interbody spacerin its low-profile configuration according to the present invention.

FIG. 2 is a rear top perspective view of the expandable interbody spacerof FIG. 1 in its low-profile configuration.

FIG. 3 is a side elevational view of the expandable interbody spacer ofFIG. 1.

FIG. 4 is a cross-sectional view of the expandable interbody spacer ofFIG. 1.

FIG. 5 is an exploded view of the expandable interbody spacer of FIG. 1.

FIG. 6 is a top perspective view of a housing of the expandableinterbody spacer according to the present invention.

FIG. 7 is a side elevational view of the housing of FIG. 6.

FIG. 8 is a top perspective view of an endplate of the expandableinterbody spacer according to the present invention.

FIG. 9A is a side elevational view of the endplate of FIG. 8.

FIG. 9B is a front elevational end view of the endplate of FIG. 8.

FIG. 10 is a bottom view of the endplate of FIG. 8.

FIG. 11 is a cross-sectional view of the endplate taken along line 11-11of FIG. 10.

FIG. 12A is a top perspective view of an anterior actuator segment ofthe expandable interbody spacer of FIG. 1.

FIG. 12B is a bottom perspective view of the anterior actuator segmentof FIG. 12A.

FIG. 12C is a bottom view of the anterior actuator segment of FIG. 12A.

FIG. 12D is a side view of the anterior actuator segment of FIG. 12A.

FIG. 12E is an end view of the anterior actuator segment of FIG. 12A.

FIG. 12F is a side view of the anterior actuator segment of FIG. 12A.

FIG. 12G is a cross-sectional view of the anterior actuator segmenttaken along line 12G-12G of FIG. 12E.

FIG. 12H is a cross-sectional view of the anterior actuator segmenttaken along line 12H-12H of FIG. 12F.

FIG. 13A is a top perspective view of a posterior actuator segment ofthe expandable interbody spacer of FIG. 1.

FIG. 13B is a bottom perspective view of the posterior actuator segmentof FIG. 13A.

FIG. 13C is a bottom view of the posterior actuator segment of FIG. 13A.

FIG. 13D is a side view of the posterior actuator segment of FIG. 13A.

FIG. 13E is an end view of the posterior actuator segment of FIG. 13A.

FIG. 13F is a side view of the posterior actuator segment of FIG. 13A.

FIG. 13G is a cross-sectional view of the posterior actuator segmenttaken along line 13G-13G of FIG. 13E.

FIG. 13H is a cross-sectional view of the posterior actuator segmenttaken along line 13H-13H of FIG. 13F.

FIG. 14A is side elevational view of an anterior threaded actuator is ofan expandable interbody spacer according to the present invention.

FIG. 14B is a cross-sectional view of the anterior threaded actuatortaken along line 14B-14B of FIG. 14A.

FIG. 15A is a side elevational view of a posterior threaded actuator ofan expandable interbody spacer according to the present invention.

FIG. 15B is a cross-sectional view of the posterior threaded actuatortaken along line 15B-15B of FIG. 15A.

FIG. 16 is a side elevational view of a driver for the expandableinterbody spacer according to the present invention.

FIG. 17A is a top view of a driver engaged with an expandable spacer forparallel expansion according to the present invention.

FIG. 17B is a cross-sectional view of a driver engaged with anexpandable spacer taken along line 17B-17B of FIG. 17A.

FIG. 18 is a top perspective view of an expandable interbody spacer inits high-profile configuration according to the present invention.

FIG. 19 is a top perspective view of an expandable interbody spacer inits high-profile configuration according to the present invention.

FIG. 20 is a side elevational view of the expandable interbody spacer ofFIG. 18.

FIG. 21 is a cross-sectional view of the expandable interbody spacer ofFIG. 18.

FIG. 22 is an anterior end view of an expandable interbody spacer in itslow-profile configuration according to the present invention.

FIG. 23 is an anterior end view of an expandable interbody spacer in itshigh-profile configuration according to the present invention.

FIG. 24 is a posterior end view of an expandable interbody spacer in itslow-profile configuration according to the present invention.

FIG. 25 is a posterior end view of an expandable interbody spacer in itshigh-profile configuration according to the present invention.

FIG. 26A is a top view of a driver engaged with an expandable spacer foranterior angular expansion according to the present invention.

FIG. 26B is cross-sectional view of a driver engaged with an expandableinterbody spacer taken along line 26B-26B of FIG. 26A.

FIG. 27 is a side elevational view of an expandable interbody spacer inits anterior angulated configuration according to the present invention.

FIG. 28 is a cross-sectional view of the expandable interbody spacer ofFIG. 27.

FIG. 29 is a side elevational view of an expandable interbody spacer inits combined configuration of anterior angulation and parallel expansionaccording to the present invention.

FIG. 30 is a cross-sectional view of the expandable interbody spacer ofFIG. 29.

FIG. 31A is a top view of a driver engaged with an expandable spacer forposterior angular expansion according to the present invention.

FIG. 31B is cross-sectional view of a driver engaged with an expandableinterbody spacer taken along line 31B-31B of FIG. 31A.

FIG. 32 is a side elevational view of an expandable interbody spacer inits posterior angulated configuration according to the presentinvention.

FIG. 33 is a cross-sectional view of the expandable interbody spacer ofFIG. 32.

FIG. 34 is a side elevational view of an expandable interbody spacer inits combined configuration of posterior angulation and parallelexpansion according to the present invention.

FIG. 35 is a cross-sectional view of the expandable interbody spacer ofFIG. 34.

DETAILED DESCRIPTION OF THE INVENTION

An expandable interbody spacer that is movable from an unexpandedconfiguration into a variety of expanded configurations includinguniform parallel expansion, anterior angulation, posterior angulationand a combination of parallel expansion and anterior or posteriorangulation is described below. FIGS. 1-4 depict an expandable interbodyspacer 10 in an unexpanded configuration. The spacer 10 is typicallyused to stabilize or fuse vertebral bodies in the lumbar or other regionof the spine. With particular reference to the exploded view of FIG. 5,the expandable interbody spacer 10 includes a housing 12, upper andlower endplates 14, an anterior actuator 16, a posterior actuator 18, ananterior drive screw 20, and a posterior drive screw 22. The expandableinterbody spacer 10 is insertable into the disc space between twoadjacent vertebral bodies from a posterior approach while in anunexpanded state illustrated in FIGS. 1-4. Generally, the unexpandedstate is characterized by a low-profile configuration in which theheight of the spacer 10 is the lowest and the endplates 14 are parallelto each other. Once inserted and properly positioned inside the discspace, both upper and lower endplates 14 are expanded in height on bothsides of the housing 12 into an expanded state. The spacer 10 has anumber of possible expanded states. The expanded states include parallelexpansion, angular expansion, or a combination of both angular andparallel expansion and, furthermore, the spacer 10 has two types ofangular expansion—anterior angular expansion and posterior angularexpansion. In the expanded state characterized by parallel expansion,the endplates 14 are moved away from the housing 12 to increase thedistance between the endplates 14 in a uniform manner such that theendplates 14 remain parallel to each other in the expanded state. Inanterior angular expansion, the height of the spacer 10 at the anteriorend, also called the distal end, is greater than the height of thespacer 10 at the posterior end, also called the proximal end. Inposterior angular expansion, the height of the spacer 10 at theposterior end is greater than the height of the spacer 10 at theanterior end. The expanded states are effected by a unique driver 23that selectively engages with the anterior drive screw 20, posteriordrive screw 22 or both. As one or both of the anterior drive screw 20and posterior drive screw 22 are engaged by the driver 23 and rotated,the anterior actuator 16, posterior actuator 18 or both are moved towedge the endplates 14 into one of the expanded states.

Turning now to the FIGS. 6-7, the housing 12 will now be described ingreater detail. The housing 12 includes two opposite sidewalls 24interconnected by two opposite endwalls 26 that together define an openinterior of the housing 12. A guidepost 28 is formed on the innersurface of each of the sidewalls 24 and opposite from each other atapproximately the midpoint. The guideposts 28 are sized and configuredto be engaged with vertical slots 62 formed on the upper and lowerendplates 14 to align and guide the endplates 14 with respect to thehousing 12. The sidewalls 24 are parallel to each other and of equallength. The endwalls 26 are parallel to each other and approximately ofequal length. Both the sidewalls and endwalls 26 define a rectangularshaped housing 12 having a top end and bottom end that open to theinterior. The top end and the bottom end are parallel to each other andthe sidewalls 24 have a constant height. The front distal endwall 26 isslightly curved and defines a threaded distal opening 30 that is sizedand configured to threadingly engage with the anterior drive screw 20.The height of the housing 12 is slightly greater in the location of thedistal threaded opening 30. The rear proximal endwall 26 includes acylindrical-like collar 34 extending proximally and defining a threadedrear opening 32 that opens to the interior of the housing 12. Thethreaded rear opening 32 is sized and configured to threadingly engagewith the posterior drive screw 22. The collar 34 includes externalthreads for connecting with a driver instrument 23 and notches 36 foraligning the connection with the driver 23. The height of the housing 12is greater in the location of the proximal threaded opening 32. The topand bottom of the proximal endwall 26 includes top and bottom flats togive the collar 34 a low-profile height.

Turning to FIGS. 8-11, the upper and lower endplates 14 will now bedescribed. The upper and lower endplates 14 are identical and areconnected to the housing 12 via the anterior and posterior actuators 16,18 and the anterior and posterior drive screws 20, 22 threaded into thehousing 12. Each endplate 14 has a bone-engaging surface 46 and aninterior surface 48 opposite from the bone-engaging surface 46. Thebone-engaging surface 46 includes a plurality of tooth-like ridges. Theridges have pointed peaks to engage and increase the purchase on theadjacent vertebra between which the spacer 12 is located. The ridges mayfurther be angled to help hold and directionally prevent migration ofthe spacer 10 relative to the adjacent vertebrae when implanted withinthe intervertebral space. The endplate 14 further includes a leadingsurface 55 that does not have tooth-like projections. The leadingsurface 55 is slightly angled to form a leading ramp-like surface at thedistal end for easier penetration and distraction of the disc space asthe spacer 10 is inserted. Each endplate 14 includes at least oneendplate opening 52 extending between the bone-engaging surface 46 andthe interior surface 48 and opening to the interior of the housing 12.The endplate opening 52 reduces the weight of the spacer 10 and permitsbone ingrowth to take place into the endplate 14. A family of bone graftmaterials, such as autograft, bone morphogenic protein (BMP), bonemarrow aspirate, concentrate, stem cells and the like, may be placedinside the endplate openings 52 and into the interior of the housing 12to promote bone growth into the spacer 10. Also, small holes may beformed in the bone-engaging surface 46 to promote osseointegration. Thebone-engaging surface 46 of the endplates 14 are substantially flat andparallel to each other when in the collapsed, low-profile unexpandedstate. The endplates 14 have a width that is approximately equal to theoverall width of the spacer 10 and approximately equal to the width ofthe housing 12. Each endplate 14 includes two oppositely-disposed andparallel side rails, a first side rail 50 a and a second side rail 50 b,extending perpendicularly from the interior surface 48. The first siderail 50 a includes an inner surface facing the longitudinal axis of theendplate 14 and an outer surface facing outwardly. The first side rail50 a is offset inwardly from the adjacent side edge of the bone-engagingsurface 46 by a first distance 47. The first side rail 50 a includes aU-shaped slot 62 a that is perpendicular to the horizontal plane. Theslot 62 a is sized and configured to receive a guidepost 28 of thehousing 12. The second side rail 50 b includes an inner surface facingthe longitudinal axis of the endplate 14 and an outer surface facingoutwardly. The second side rail 50 b is offset inwardly from theadjacent side edge by a second distance 49 wherein the second distance49 is greater than the first distance 47. The second side rail 50 bincludes a U-shaped slot 62 b that is perpendicular to the horizontalplane. The slot 62 b is sized and configured to receive a guidepost 28of the housing 12. The slots 62 a, 62 b are oppositely disposed andaligned with each other. The endplate 14 further includes an anteriorramp 58 and a posterior ramp 60. The anterior ramp 58 is locatedproximal to the anterior end of the endplate 14. The anterior ramp 58extends at an angle from the interior surface 48 of the endplate 14. Theangle of the anterior ramp 58 is such that the height of the anteriorramp 58 increases toward the posterior end of the endplate 14 as clearlyshown in FIG. 11. The anterior ramp 58 is U-like in shape with theopening of U-shape facing the center of the endplate 14. The posteriorramp 60 is located proximal to the posterior end of the endplate 14. Theangle of the posterior ramp 60 is such that the height of the posteriorramp 60 increases toward the anterior end of the endplate 14 as clearlyshown in FIGS. 5 and 11. The posterior ramp 60 is also U-like in shapewith the opening of the U-shape facing the center of the endplate 14.The top ends of the U-shaped ramps 58, 60 meet and are aligned with theslots 62 a, 62 b. A first gap or channel 64 is defined and formedbetween the first side rail 50 a and the anterior and posterior ramps58, 60 as can be seen in FIGS. 9B and 10. The first channel 64 is sizedand configured to receive the second side rail 50 b of the lowerendplate 14. As previously mentioned, the upper and lower endplates 14are identical. Due to the offset distances 47, 49 of the side rails 50a, 50 b, the second side rail 50 b of the lower endplate 14 will bereceived inside the first channel 64 adjacent to the inner surface ofthe first rail 50 a of the upper endplate 14 to interlock the upper andlower endplates 14. A second gap or channel 66 is defined and formedbetween the second side rail 50 b and the adjacent side edge of theendplate 14. The second channel 66 can be seen in FIG. 10. The secondchannel 66 is located within the second distance 49. The second channel66 is sized and configured to receive first side rail 50 a of the lowerendplate 14. Due to the offset distances 47, 49 of the side rails 50 a,50 b, the first side rail 50 a of the lower endplate 14 will be receivedinside the second channel 66 adjacent to the outer surface of the secondrail 50 b of the upper endplate 14 to interlock the upper and lowerendplates 14. With particular reference to FIGS. 5 and 10, the first andsecond channels 64, 66 are grooves formed into the interior surface 48of the endplate 14 and are slightly longer in length than the length ofthe side rails 50 a, 50 b in order to accommodate the siderails 50 a, 50b during angulation. Formed within the first channel 64 is an anteriorindent 68 and a posterior indent 70 sized and configured to receive aportion of the anterior and posterior actuators 16, 18, respectively.There is no gap or channel between the anterior and posterior ramps 58,60 and the second side rail 50 b. The inner surface of the second siderail 50 b includes an anterior projection 72 and a posterior projection74 shown in FIGS. 5, 9B, 10 and 11. The anterior projection 72 extendsoutwardly from the inner surface of the second side rail 50 b toward thelongitudinal axis of the endplate 14. The anterior projection 72 isangled parallel to the angle of the anterior ramp 58. The anteriorprojection 72 is spaced apart from the anterior ramp 58 surface definingan anterior recess 76 therebetween. The anterior recess 76 is sized andconfigured to receive and guide part of the anterior actuator 16 whichwill be described in greater detail below. The posterior projection 74extends outwardly from the inner surface of the second side rail 50 btoward the longitudinal axis of the endplate 14. The posteriorprojection 74 is angled parallel to the angle of the posterior ramp 58.The posterior projection 74 is spaced apart from the posterior ramp 60surface defining a posterior recess 78 therebetween. The posteriorrecess 78 is sized and configured to receive and guide part of theposterior actuator 18 which will be described in greater detail below.The interior surface 48 of the endplate 14 includes a concave area 82that corresponds to and accommodates the convex surface of the distalendwall 26 of the housing 12 in the location of the distal threadedopening 30. The concave area 82 provides the spacer 10 with alow-profile configuration while allowing for a larger anterior drivescrew to be utilized. The posterior end of the endplate 14 includes acutout 80 that is sized and configured to clear the proximal collar 34of the housing 12 during angulation of the anterior end and to providethe spacer 10 with the lowest profile, largest bone-engaging surface 46,largest posterior drive screw 22 for strength and a greater range ofangulation. With particular reference to FIGS. 5, 10 and 11, theendplate 14 further includes a rectangular-shaped anterior well 84 thatis sized and configured to receive part of the anterior actuator 16 whenthe spacer 10 is in the unexpanded state. The endplate 14 also includesa rectangular-shaped posterior well 86 that is sized and configured toreceive part of the posterior actuator 18 when the spacer 10 is in theunexpanded state. The wells 84, 86 are depressions formed into theinterior surface 48 of the endplate 14 that permits the actuators 16, 18a larger range of translation providing a lower profile in theunexpanded state compared to the absence of such wells 84, 86.

Turning now to FIGS. 12A-12H, the anterior actuator 16 will now bedescribed in greater detail. The anterior actuator 16 comprises of twoidentical anterior actuator segments 88 wherein one anterior actuatorsegment 88 is inverted with respect to the other anterior actuatorsegment 88 and mated therewith. With reference back to FIG. 5, an upperanterior actuator segment 88 is adjacent to the upper endplate 14 and alower anterior actuator segment 88 is adjacent to the lower endplate 14.The upper anterior actuator segment 88 together with the lower anterioractuator segment 88 form the anterior actuator 16.

With continued reference to FIGS. 12A-12H, the anterior actuator segment88 includes a leading surface 90, a trailing surface 92, a landingsurface 94, a front wall 96, a rear wall 98, and an inner surface 100all integrally interconnected by a first sidewall 102 and a secondsidewall 104. The leading surface 90 includes a scallop 106 sized andconfigured to accommodate part of the anterior drive screw 20. Thescallop 106 corresponds to the U-shaped anterior ramp 58 and defines acontact area of the leading surface 90 that corresponds substantially tothe contact area of the anterior ramp 58. The leading surface 90 isangled. The angle of the leading surface 90 corresponds to the angle ofthe anterior ramp 58 such that ideal mating contact is maintained duringexpansion of the spacer 10 for a uniform distribution of forces whenloaded in situ. The angled leading surface 90 is sized and configured tocontact the anterior ramp 58 of the endplate 14 and slide along theanterior ramp 58 to move the endplate 14 into expansion or reduction asthe anterior drive screw 20 is threadingly translated. The trailingsurface 92 is angled toward the vertical rear wall 98 to provide atapered actuator segment 88. The landing surface 94 is substantiallyrectangular in shape and includes a notch in the location of the sidechannel 108. The landing surface 94 is flat, horizontally orientated andsized and configured to fit inside the anterior well 84 of the endplate14. The front wall 96 is vertical and substantially parallel to the rearwall 98. The first sidewall 102 and second sidewall 104 are parallel toeach other and vertical in orientation. The first sidewall 102 includesa side channel 108 having an angle equal to the angle of the leadingsurface 90. The side channel 108 is sized and configured to receive theanterior projection 72 of the endplate 14 within the side channel 108.The anterior projection 72 when mated with the side channel 108 servesto hold the endplates 14 and anterior actuator 16 together and inposition and also serves to guide the movement of the anterior actuator16 along the anterior ramp 58. The first sidewall 102 includes a curvedprojection 110 that is sized and configured to mate with a curvedindentation 112 on the second sidewall 104 of an adjacent and up-sidedown-oriented anterior actuator segment 88 comprising the anterioractuator 16. The inner surface 100 is curved to match the curvature ofthe ball head of the anterior drive screw 20. The inner surface 100 isspherical in shape and, in particular, it is semi-spherical in shape andfurther it is truncated and semi-spherical in shape.

As mentioned previously, the upper anterior actuator segment 88 isidentical to the lower anterior actuator segment 88 and that togetherthey are joined to form the anterior actuator 16. One of the twoidentical anterior actuator segments 88 of the anterior actuator 16 isturned upside down or inverted such that the inner surfaces 100 faceeach other. The lower anterior actuator segment 88 is adjacent to thelower endplate 14 and the upper anterior actuator segment 88 is adjacentto the upper endplate 14. As can be seen in FIG. 5, the first sidewall102 of the lower anterior actuator segment 88 faces the second side rail50 b of the lower endplate 14 and, as such, the side channel 108 of thelower actuator segment 88 engages with the anterior projection 72 of thelower endplate 14 whereas the first sidewall 102 of the upper anterioractuator segment 88 is on the opposite side and faces the second siderail 50 b of the upper endplate 14 and, as such, the side channel 108 ofthe upper actuator segment 88 engages with the anterior projection 72 ofthe upper endplate 14. The curved projection 110 of the upper anterioractuator segment 88 mates with the curved indentation 112 of the loweranterior actuator segment 88 on one side and the curved projection 110of the lower anterior actuator segment 88 mates with the curvedindentation 112 of the upper anterior actuator segment 88. The matedupper and lower anterior actuator segments 88 form a clamshell-likechamber that captures the anterior drive screw 20. The ball head 118 ofthe anterior drive screw 20 is located between the upper anterioractuator segment 88 and the lower anterior actuator segment 88 andcaptured inside the clamshell-like enclosure such that the curved,spherical ball head 118 of the anterior drive screw 20 may make contactwith the truncated spherical ball shape chamber comprised of the innersurfaces 100 of the adjacent upper and lower anterior actuator segments88 as needed for the transmission of load from the endplates 14 to theactuator 16 to the drive screw 20 and, in turn, to the housing 12 whilepermitting the drive screw 20 to rotate about its axis relative to theanterior actuator 16. The leading surfaces 90 of the upper and loweranterior actuator segments 88 face toward the proximal end and areangled such that the distance between the leading surfaces 90 increasestowards the distal end. With particular reference to FIG. 12H, the firstsidewall 102 depends downwardly or otherwise extends in the location ofthe curved projection 110 such that the curvature of the spherical innersurface 100 is longer than a semi-circle to define an overhang 114wherein the slope of a plane tangential to the cross-sectional curvegoes from a negative value to a positive value in the location of thecurved projection 110. This overhang 114 advantageously causes the ballhead 118 of the drive screw 20 to snap in position past the overhangs114 of both anterior actuator segments 88 and to be held in place by theoverhangs 114.

Turning now to FIGS. 13A-13H, the posterior actuator 18 will now bedescribed in greater detail wherein like numbers are used to describelike parts. The posterior actuator 18 is comprised of two identicalposterior actuator segments 116 wherein one posterior actuator segment116 is inverted with respect to the other posterior actuator segment 116and mated therewith. With reference back to FIG. 5, an upper posterioractuator segment 116 is adjacent to the upper endplate 14 and a loweranterior actuator segment 116 is adjacent to the lower endplate 14. Theupper anterior actuator segment 116 together with the lower anterioractuator segment 116 form the anterior actuator 18.

With continued reference to FIGS. 13A-13H, the posterior actuatorsegment 116 includes a leading surface 90, a trailing surface 92, alanding surface 94, a front wall 96, a rear wall 98, and an innersurface 100 all integrally interconnected by a first sidewall 102 and asecond sidewall 104. The leading surface 90 includes a scallop 106 sizedand configured to accommodate part of the posterior drive screw 22. Thescallop 106 corresponds to the U-shaped posterior ramp 60 and defines acontact area of the leading surface 90 that corresponds substantially tothe contact area of the posterior ramp 60. The leading surface 90 isangled. The angle of the leading surface 90 corresponds to the angle ofthe posterior ramp 60 such that ideal mating contact is maintainedduring expansion of the spacer 10 for a uniform distribution of forceswhen loaded in situ. The angled leading surface 90 is sized andconfigured to contact the posterior ramp 60 of the endplate 14 and slidealong the posterior ramp 60 to move the endplate 14 into expansion orreduction as the posterior drive screw 22 is threadingly translated. Thetrailing surface 92 is angled toward the vertical rear wall 98 toprovide a tapered actuator segment 116. The landing surface 94 issubstantially rectangular in shape and includes a notch in the locationof the side channel 108. The landing surface 94 is flat, horizontallyorientated and sized and configured to fit inside the posterior well 86of the endplate 14. The front wall 96 is vertical and substantiallyparallel to the rear wall 98. The first sidewall 102 and second sidewall104 are parallel to each other and vertical in orientation. Unlike theanterior actuator segment 88, the second sidewall 104 of the posterioractuator segment 116 includes a side channel 108 having an angle equalto the angle of the leading surface 90. The side channel 108 is sizedand configured to receive the posterior projection 74 of the endplate 14within the side channel 108 having the same angle. The posteriorprojection 74 when mated with the side channel 108 serves to hold theendplates 14 and posterior actuator 18 together and in position and alsoserves to guide the movement of the posterior actuator 18 along theposterior ramp 60. The first sidewall 102 includes a curved projection110 that is sized and configured to mate with a curved indentation 112on the second sidewall 104 of an adjacent and up-side down-orientedposterior actuator segment 116 comprising the posterior actuator 18. Theinner surface 100 is curved to match the curvature of the ball head ofthe posterior drive screw 22. The inner surface 100 is spherical inshape and, in particular, it is semi-spherical in shape and further itis truncated and semi-spherical in shape.

As mentioned previously, the upper posterior actuator segment 116 isidentical to the lower posterior actuator segment 116 and that togetherthey are joined to form the posterior actuator 18. One of the twoidentical posterior actuator segments 116 comprising the posterioractuator 18 is turned upside down or inverted such that the innersurfaces 100 face each other. The lower posterior actuator segment 116is adjacent to the lower endplate 14 and the upper posterior actuatorsegment 116 is adjacent to the upper endplate 14. As can be seen in FIG.5, the second sidewall 104 of the lower posterior actuator segment 116faces the second side rail 50 b of the lower endplate 14 and as such theside channel 108 of the lower actuator segment 116 is oriented to engagewith the posterior projection 74 of the lower endplate 14; whereas, thesecond sidewall 104 of the upper posterior actuator segment 116 is onthe opposite side and faces the second side rail 50 b of the upperendplate 14 and as such the side channel 108 of the upper actuatorsegment 88 engages with the posterior projection 74 of the upperendplate 14. The curved projection 110 of the upper posterior actuatorsegment 116 mates with the curved indentation 112 of the lower posterioractuator segment 116 on one side and the curved projection 110 of thelower posterior actuator segment 116 mates with the curved indentation112 of the upper posterior actuator segment 116 on the other side toform a clamshell-like chamber that captures the posterior drive screw 22therebetween. The spherical-shaped ball head 118 of the posterior drivescrew 22 is located between the upper posterior actuator segment 116 andthe lower posterior actuator segment 116 and captured inside theclamshell-like enclosure such that the curved, spherical ball shape ofthe posterior drive screw 20 may polyaxially make contact with thetruncated spherical ball shape chamber comprised of the inner surfaces100 of the adjacent upper and lower posterior actuator segments 116 forthe transmission of load from the endplates 14 to the actuator 18 to thedrive screw 20 and to the housing 12 while permitting the drive screw 22to rotate about its axis relative to posterior actuator 18. The leadingsurfaces 90 of the upper and lower posterior actuator segments 116 facetoward the distal end and are angled such that the distance between theleading surfaces 90 increases towards the proximal end. With particularreference to FIG. 13H, the first sidewall 102 depends downwardly orotherwise extends at the curved projection 110 such that the curvatureof the spherical inner surface 100 is longer than a semi-circle todefine an overhang 114 wherein the slope of a plane tangential to thecross-sectional curve goes from a negative value to a positive value inthe location of the curved projection 110. This overhang 114advantageously causes the ball head 118 of the drive screw 22 to snap inposition past the overhangs 114 of both posterior actuator segments 116and to be held in place by the overhangs 114.

Turning now to FIGS. 14A-14B, the anterior drive screw 20 will now bedescribed. The anterior drive screw 20 includes a ball head 118 at aproximal end connected to a threaded shank portion 120 that extendstoward a distal end. The ball head 118 has a spherical shape that istruncated at the shaft 120. The diameter of ball head 118 is larger thanthe diameter of the threaded shank 120. A neck portion 122 withoutthreads is located between the ball head 118 and the shank 120. As canbe seen in FIG. 14B, the anterior drive screw 20 includes a drive bore124 that extends between the proximal end and the distal end of thedrive screw 20. The drive bore 124 extends along the entire length ofthe drive screw 20 and has a proximal opening in the ball head 118 atthe proximal end and a distal opening in the threaded shank 120 at thedistal end. In one variation, the drive bore 124 does not have a distalopening in the threaded shank 120. The drive bore 124 has a hexalobeshape (visible in FIG. 5) or hexagonal shape in cross-section along theentire length of the bore 124. The drive bore 124 is sized andconfigured to be engaged to rotate the drive screw 20 by the driverinstrument 23. The bore 124 may have any non-circular cross-sectionalshape that is corresponds to and is sized and configured to mate with tothe cross-sectional shape of distal drive portion of the driverinstrument 23.

Turning now to FIGS. 15A-15B, the posterior drive screw 22 will now bedescribed wherein like reference numbers are used to describe likeparts. The posterior drive screw 22 includes a ball head 118 at thedistal end connected to a threaded shank portion 120 that extends towardthe proximal end. The ball head 118 has a shape that is truncated at theshaft 120. The diameter of ball head 118 is larger than the diameter ofthe threaded shank 120. A neck portion 122 without threads is locatedbetween the ball head 118 and the shank 120. As can be seen in FIG. 15B,the posterior drive screw 22 includes a drive bore 124 that extendsbetween the proximal end and the distal end of the drive screw 22. Thedrive bore 124 extends along the entire length of the drive screw 22 andhas a proximal opening in the threaded shank 120 at the proximal end anda distal opening in the ball head 118 at the distal end. The drive bore124 has a hexalobe shape (visible in FIG. 5) or hexagonal shape incross-section along the entire length of the bore 124. The drive bore124 is sized and configured to be matingly engaged for rotation by thedriver instrument 23. The bore 124 may have any non-circularcross-sectional shape that is corresponds to and is sized and configuredto mate with to the cross-sectional shape of the proximal drive portionand distal drive portion of the driver instrument 23. A non-circularcross-section will have a major diameter and minor diameter.

With reference to both FIGS. 14A-14B and FIGS. 15A-15B, the threadedshanks 120 of the anterior and posterior drive screws 20, 22 have thesame length, the same size thread and the same number of threads perinch. The helical threaded shank 120 of the posterior drive screw 22 hasa right-handed thread; whereas, the helical threaded shank 120 of theanterior drive screw 20 has a left-handed thread. This difference inhandedness of the threads is clearly visible in FIGS. 14A and 15A. Inanother variation, the helical threaded shank 120 of the posterior drivescrew 22 has a left-handed thread; whereas, the helical threaded shank120 of the anterior drive screw 20 has a right-handed thread. Inessence, the helical direction of one of the two drive screws 20, 22 isopposite in direction from the other. Viewing from one of the proximalend or distal end, the direction of translation with respect to thehousing 12 of one of the anterior drive screw 20 and posterior drivescrew 22 is positive and the direction of translation of the other oneof the anterior drive screw 20 and posterior drive screw 22 is negative.The advantage of this difference will be described in greater detailbelow.

Turning now to FIG. 16, there is shown the driver instrument 23according to the present invention. The driver 23 includes a handle 126at the proximal end. The driver 23 further includes a proximal driveportion 128 having a length and distal drive portion 130 having a lengthseparated by a middle portion 132 having a length. The handle 126 mayinclude a neck portion 134 between the handle 126 and the proximal driveportion 128. The distal drive portion 130 is located at the distal endof the driver 23 and extends proximally toward the middle portion 132.The proximal drive portion 128 is located near the handle 126 andextends proximally from the middle portion 132 towards the handle 126 orneck portion 134 if a neck portion 134 is defined. The proximal anddistal drive portions 128, 130 have a mating cross-section that is sizedand configured to engage with drive bores 124 of the anterior andposterior drive screws 20, 22, respectively, in order to rotate theanterior and posterior drive screws 20, 22. The cross-sectional shape ofthe proximal and distal drive portions 128, 130 are uniform and extendalong their entire respective lengths. The distal drive portion 130 hasa cross-section that is sized and configured to also engage with thedrive bore 124 of the posterior drive screw 22. In one variation, all ofthe drive bores 124 have the same cross-sectional shape and the driveportions 128, 130 have the same corresponding cross-sectional shape and,in another variation, have the same diameter. For example, in onevariation, the drive bores 124 have a hexalobe shape as shown in FIGS.14-15 and the driver 23 has proximal and distal drive portion 128, 130that also have a hexalobe shape sized and configured to engage the drivescrews 20, 22 for rotation. The diameters of the proximal and distaldrive portions 128, 130 are the same to match the diameters of the drivebores 124 and are greater in diameter than the diameter of the middleportion 132. The middle portion 132 does not have an outer surface sizedand configured to engage any drive bores 124 into rotation. In anothervariation, the middle portion has a smooth circular cross-section andmiddle diameter that is the same as the diameter or inner diameter ofthe drive bores 124. The diameter of the handle 126 is greater than thediameter of the drive portions 128, 130 and, if a neck portion 134 isprovided, the neck portion 134 has a diameter greater than the driveportions 128, 130. The neck portion 134 does not have an outer surfaceor cross-sectional shape configured to engage any of the drive screws20, 22. The handle 126 or neck portion 134 serves as an abutment or stopfor the insertion of the driver 23. If there is no neck portion 134, thehandle 126 will serve as an abutment. The distal drive portion 130 ofthe driver 23 is sized and configured such that it can be inserted firstinto the posterior drive screw 22 and passed distally into the spacer 10into the anterior drive screw 20 until the neck portion 134 or handle126, because of its larger diameter, abuts the proximal end of theposterior drive screw 20 or spacer 10 and, thereby, the driver 23 isprevented from further insertion into the spacer 10. The proximal driveportion 128, the middle portion 132 and the distal drive portion 130altogether define the active portion 136 of the driver 23 and theircombined lengths or the length of the active portion 136 is not longerthan the length of the spacer 10. If the active length 136 of the driver23 is longer than the spacer 10, the distal end of the driver 23 wouldextend beyond the length of the spacer 10 when the handle 126 is abuttedat the proximal end and potentially impinge on surrounding tissue.Hence, the neck portion 134 serves as an abutment that simplifies theinsertion of the driver 23 by allowing the user to insert the driver 23until abutment is made with the neck portion without fear of the driver23 extending beyond the distal end of spacer 10.

The driver 23 is configured such that the distal drive portion 130engages the anterior drive screw 20 and the proximal drive portion 128engages the posterior drive screw 22 simultaneously when the spacer 10is in the collapsed, low-profile configuration in order to rotate bothof the drive screws 20, 22 simultaneously. The driver 23 is alsoconfigured to be pulled back in the proximal direction such that theproximal drive portion 128 is disengaged from the posterior drive screw22 while the distal drive portion 130 remains engaged with the anteriordrive screw 20 to effect variable angulation of the anterior end of thespacer 10. When the spacer 10 is in the collapsed, low-profileconfiguration, the drive screws 20, 22 will be at the farthest distanceapart from each other. Hence, the middle portion 132 is longer than thedistance between the drive screws 20, 22 when in the collapsedlow-profile configuration so that the driver 23 may be pulled back inthe proximal direction to disengage the proximal drive portion 128 fromthe posterior drive screw 22 while the distal drive portion 130 stillengages with the anterior drive screw 20. The length of the activeportion 136 or the combined length of the distal drive portion 130,proximal drive portion 128 and middle portion 132 is approximately equalto the length of the spacer 10. The length of the proximal drive portion128 is shorter than the length of the distal drive portion 130. Giventhese parameters and to reduce the torque required to rotate the drivescrews 20, 22, the length of the distal drive portion 130 isapproximately equal to the length of the anterior drive screw 20 and thelength of the proximal drive portion 22 is shorter than the length ofthe posterior drive screw 22. In one variation, the distal drive portion130 is equal to the length of the anterior drive screw 20, the proximaldrive portion 128 is ⅘ the length of the posterior drive screw 22 andthe middle portion 132 is 5/4 longer than the length of the distancebetween the two drive screws 20, 22 when the spacer 10 is in thecollapsed low-profile configuration. The drive portions 128 and 130 arecoaxial.

The expandable interbody spacer 10 is assembled by placing one endplate14 such that the interior surface 48 faces upwardly defining a lowerendplate 14. One anterior actuator segment 88 is placed into theanterior well 84 of the lower endplate 14 such that the anteriorprojection 72 of the lower endplate 14 is received inside the sidechannel 108 of the anterior actuator segment 88. One posterior actuatorsegment 116 is placed into the posterior well 86 of the lower endplate14 such that the posterior projection 74 of the endplate 14 is receivedinside the side channel 108 of the posterior actuator segment 116. Theanterior drive screw 20 is threaded into the distal threaded opening 30of the housing 12 and the posterior drive screw 22 is threaded into therear threaded opening 32. The guideposts 28 of the housing 12 arealigned with the slots 62 of the lower endplate 14. The drive screws 20,22 may be threaded to adjust their alignment such that the ball heads118 are received inside the inner surface 100 of the anterior andposterior actuator segments 88, 116. A second anterior actuator segment88 is connected to the upper endplate 14 by inserting the anteriorprojection 72 into side channel 108 of the second anterior actuatorsegment 88. A second posterior actuator segment 116 is connected to theupper endplate 14 by inserting the posterior projection 74 into the sidechannel 108 of the second posterior actuator segment 116. The upperendplate 14 is aligned so that the slots 62 of the upper endplate 14receive the guideposts 28 of the housing 12 and that the actuatorsegments 88, 116 connected to the upper endplate 14 cover the ball heads118 of the drive screw 20, 22. Pressure is applied such that theoverhangs 114 of the actuator segments 88, 116 snap over the ball heads118.

In use, the present expandable interbody spacer 10 is inserted into thedisc space between adjacent vertebral bodies. The spacers 10 of FIGS.1-29 are generally configured for use as a PLIF cage in spinal surgicalprocedures. It is understood that novel features of the presentinvention can find application in different types of spacers includingbut not limited to interbody spacers for PLIF, TLIF, XLIF surgicalprocedures as well as other types of orthopedic implants.

Implanting the interbody spacer 10 involves removal, in whole or inpart, of the disc material from the intervertebral space at the targetvertebral level where the interbody spacer 10 will be implanted. Thepatient is oriented to provide some distraction of the disc space and toprovide access to the spine. Additional distraction of the disc spaceand surrounding tissues may be needed to decompress the nerve roots,realign the anatomical axis of the spine, and restore disc space heightat the particular target level. After disc material is removed, a cleanspace is achieved in which to place the device. The vertebral endplatesmay be further prepared using burrs, curettes and the like to abrade andclean the endplates to encourage bone regeneration.

A surgeon will then connect the spacer 10 for to an insertion instrument(not shown). The insertion instrument is aligned with the spacer 10 viathe notches 36 and connected at the proximal end of the spacer 10 suchthat it is secured to the collar 34 by threadingly engaging theinsertion instrument around the collar 34. The driver 23 is configuredto be inserted into one or more of the anterior drive screw 20 andposterior drive screw 22 by aligning the distal and proximal driveportions within the selected one or more drive bores 124 as will bedescribed in greater detail below. The surgeon uses the insertioninstrument to grasp the spacer 10 and place it at the mouth of theintervertebral space in its low-profile configuration. The spacer 10 ismoved and orientated into its proper location within the intervertebralspace. Bone graft or other material may be placed inside the interior ofthe spacer 10 through the endplate openings 52 prior the insertion ofthe spacer 10 into the disc space. The bone graft material promotesingrowth and improves blood supply in order to grow active and live bonefrom the adjacent spinal vertebrae to inter-knit with the spacer 10 and,thereby, eventually immobilize and fuse the adjunct spinal vertebrae.

The spacer 10 is placed such that the upper endplate 14 contacts thelower endplate of the upper vertebral body and the lower endplate 14 ofthe spacer 10 contacts the upper endplate of the lower vertebral body oneither side of the target intervertebral space. The geometry of theteeth on the bone-engaging surface 46 provides resistance to migrationof the spacer 10 while inside the target space. Other coatings andsurface textures may also be provided on the spacer 10. When the spacer10 is in position, the driver 23 is connected to the spacer 10 to deploythe spacer 10 into its expanded or high-profile configuration. Theinsertion instrument may be disconnected and removed when needed.

Turning now to FIGS. 17-25, uniform parallel expansion of the spacer 10will now be described. The spacer 10 is inserted into the disc spacewhile it is in an unexpanded, collapsed state. The unexpanded state isillustrated in FIGS. 1-4, 22 and 24. The distal end of the driver 23 isinserted into the drive bore 124 of the posterior drive screw 22 andmoved in a distal direction relative to the spacer 10 until the distaldrive portion 130 of the driver 23 is completely inserted into the drivebore 124 of the anterior drive screw 20 while the spacer 10 is in anunexpanded, low profile configuration as shown in FIGS. 17A-17B. Whenthe distal drive portion 130 is aligned with the anterior drive screw20, such that the length of the distal drive portion 130 is residentwithin the length of the anterior drive screw 20, the proximal driveportion 128 will be advantageously aligned with the posterior drivescrew 22 such that the hexalobe cross-section of the posterior drivescrew 22 engages the hexlobe cross-section of the drive bore 124. Thedrive bore 124 is formed along the entire length of each drive screw 20,22 and each drive screw 20, 22 has proximal and distal openings. Theinsertion of the driver 23 into the spacer 10 is facilitatedadvantageously by the drive screws 20, 22 and their respective drivebores 124 being aligned with each other coaxially along a drive axis.Because of the corresponding hexalobe cross-sectional shape of the drivebores 124 and drive portions, the driver 23 is easily inserted into boththe anterior and posterior drive screws 20, 22 with a minimum ofrotation of the driver 23 for alignment purposes before the distal driveportion 128 enters the anterior drive screw 20. Furthermore, insertionof the driver 23 into a position for parallel expansion is facilitatedby the neck portion 134 of the driver 23 which has a diameter largerthan the diameter of the drive bore 124. The user simply inserts thedriver 23 until the neck portion 134 abuts against the posterior drivescrew 22. If a driver 23 variation without a neck portion 134 is used,the handle 126, having a larger diameter than the posterior drive screw22, will abut the drive screw 22. The neck portion 134 advantageouslyallows the driver 23 to have a longer in length while at the same timeproviding a low-profile and a substantial handle 126 of increaseddiameter to the driver 23 to fit a surgeon's hand. The active portion136 of the driver 23 is approximately equal to the length of the spacer10. The neck portion 134 or handle 126, if an intermediate diameter neckportion 134 is not employed, advantageously serves as a stop preventinginsertion of the driver 23 beyond a distance of approximately the lengthof the spacer 10. This stop advantageously prevents the distal end ofthe driver 23 from protruding beyond the approximate distal end of thespacer 10. Furthermore, the neck portion 134 allows the surgeon toeasily and quickly insert the driver 23 into the spacer 10 all the wayuntil abutment is made with the enlarged diameter of the neck portion134 or handle 126. Also, advantageously, the interior of the spacer 10provides a clear pathway for the passage of the driver 23 between thetwo drive screws 20, 22 as the spacer 10 is configured so that there areno impeding mechanical or anatomical structures that would interferewith clear passage of the driver 23. When the driver 23 is inserted forparallel expansion as shown in FIG. 17B, the distal drive portion 130will be automatically aligned within the drive bore 124 of the anteriordrive screw 20 and the proximal drive portion 128 will be automaticallyaligned within the drive bore 124 of the posterior drive screw 22 andthe middle portion 132 will be located between the two drive screws 20,22. As mentioned previously, the length of the distal drive portion 130is approximately the same length as the length of the anterior drivescrew 20 to provide the user with maximum torqueing advantage. Thelength of the proximal drive portion 128 is shorter than the length ofthe posterior drive screw 22 and the middle portion 132 is longer thanthe distance between the drive screws 20, 22 when the spacer 10 is inthe unexpanded. When the driver 23 is in position for parallel expansionas shown in FIG. 17B, the driver 23 is rotated in one of a clockwisedirection or counterclockwise direction to bring the spacer 10 into anexpanded state. When the driver 23 is rotated, the posterior drive screw22 is rotated. As the posterior drive screw 22 is rotated, the threadson the threaded shank 120 engage the complementary threads on the rearthreaded opening 32 of the housing 12 allowing the posterior drive screw22 to translate distally with respect to the housing 12 due to theright-handedness of the threads of the posterior drive screw 22 asviewed from the proximal end of the spacer 10. As the posterior drivescrew 22 moves distally, it moves the posterior actuator 18 distallyalong with it. The leading surfaces 90 of upper and lower posterioractuator segments 116 will contact the posterior ramps 60 and slidealong the posterior ramps 60 to wedge the upper and lower endplates 14apart causing the endplates 14 at the proximal end to separate andincrease in height. Simultaneously, when the driver 23 is rotated in thesame direction, the threads on the threaded shank 120 of the anteriordrive screw 20 engage the complementary threads on the distal threadedopening 30 of the housing 12 causing the anterior drive screw 20 to movein a proximal direction with respect to the housing 12 due to theleft-handedness of the threads of the anterior drive screw 20. As theanterior drive screw 20 moves proximally, it moves the anterior actuator16 proximally along with it. The leading surfaces 90 of upper and loweranterior actuator segments 88 contact the anterior ramps 58 and slidealong the anterior ramps 58 to wedge the upper and lower endplates 14apart causing the endplates 14 at the distal end of the spacer 10 toseparate and increase in height. Hence, the drive screws 20, 22advantageously move in opposite directions from each other, inparticular, towards each other to effect expansion of the endplates 14increasing the distance of the spacer 10 uniformly on both sidessimultaneously as both the upper and lower endplates 14 move away fromthe housing 12 when the driver 23 is rotated in the same direction. Thespacer 10 in a condition of uniform parallel expansion is shown in FIGS.18-21, 23 and 25. The degree of expansion is variable with rotation ofthe driver 23 and the surgeon may advantageously select the desiredheight of the spacer 10 according to patient anatomy by rotating thedriver 23 to expand the spacer 10 as much as needed. Also, rotation ofthe driver 23 in the opposite direction reduces the height of spacer 10at both ends simultaneously. The forces exerted onto the endplates 14from the weight of the spinal column are distributed along two drivescrews 20, 22 and, hence, there is less friction on the threads of onedrive screw requiring less torque to increase or decrease the height ofthe spacer 10. Incremental rotation in either direction increases ordecreases the height as needed. Both the upper and the lower endplates14 are wedged apart by both actuators 16, 18 and the endplates 14 moveaway from the longitudinal axis of the spacer 10 uniformly. The ballheads 118 of the drive screws 20, 22 face the center of the spacer 10and their threaded shafts 120 face the distal and proximal ends of thespacer 10, respectively. Advantageously, both drive screws 20, 22 can berotated from the insertion end which is the proximal end of the spacer10.

Turning now to FIGS. 26-28, anterior angular expansion of the spacer 10will now be described. When the spacer 10 is inserted into theanatomical disc space while it is in an unexpanded, collapsed state,typically with the use of an insertion instrument (not shown) alignedwith the notches 36 and threaded to the collar 32 of the housing 12. Thespacer 10 is inserted in its unexpanded state in order to provide theleast invasive approach. Of course, according to surgeon preference, thedisc space may be distracted prior to insertion of the spacer 10 and thespacer 10 may be in a semi-expanded configuration, either in angled orparallel expansion. The spacer 10 may be inserted into the disc spacewhile spacer 10 is in a posterior angled configuration in order to helpdistract the disc space during insertion of the spacer 10. The posteriorangled configuration will be described in greater detail below. Theunexpanded state is illustrated in FIGS. 1-4, 22 and 24. While thespacer 10 is, preferably in an unexpanded, low profile configuration,the distal end of the driver 23 is mated and inserted into the drivebore 124 of the posterior drive screw 22 and moved in a distal directionrelative to the spacer 10 until the distal drive portion 130 of thedriver 23 is inserted into the drive bore 124 of the anterior drivescrew 20. The driver 23 is not inserted all the way until abutment withthe neck portion 134 is achieved. Instead, insertion of the driver 23 isarrested at a position prior to the proximal drive portion 128 enteringthe posterior drive screw 22 so that the hexalobe-shaped, bore-engagingcross-section of the proximal drive portion 128 is not engaged with thehexalobe-shaped, driver-engaging cross-section of the drive bore 124 ofthe posterior drive screw 22 as shown in FIGS. 26A-26B. This partialinsertion leaves the posterior drive screw 22 completely disengaged fromthe driver 23 and only part of the length of the distal drive portion130 engaged with the anterior drive screw 20. As a result, when thedriver 23 is rotated in one of a clockwise direction or counterclockwisedirection to bring the spacer 10 into an expanded state, the anteriordrive screw 20 will only be rotated and the posterior drive screw 22will not be rotated because in the anterior expansion position, themiddle portion 132 having a smaller diameter or a smooth, non-engaging,circular cross-section will be resident along the entire length of theposterior drive screw 20. Hence, when the driver 23 is rotated, theposterior drive screw 22 will not be rotated and, thereby, remainstationary with respect to the housing 12. However, when the driver 23is rotated, the anterior drive screw 20 will move in a proximaldirection with respect to the housing 12 due to the left-handedness ofthe threads of the anterior drive screw 20. As the anterior drive screw20 moves proximally, it moves the anterior actuator 16 proximally alongwith it. The leading surfaces 90 of the upper and lower anterioractuator segments 88 will contact the anterior ramps 58 and slide alongthe anterior ramps 58 to wedge the upper and lower endplates 14 apartbringing the anterior/distal end of the spacer 10 into an expandedcondition forming an angle relative to the un-expanded height of theposterior/proximal end. In anterior angular expansion, the anteriordrive screw 20 moves proximally. Only the distal end of the spacer 10will increase in height as both the upper and lower endplates 14 arewedged apart uniformly oppositely from the longitudinal axis of thespacer 10; whereas, the posterior/proximal end of the spacer 10 willremain in an unexpanded state creating an angle of the upper endplate 14and lower endplate 14 with respect to the housing 12. The spacer 10 inanterior angular expansion is shown in FIGS. 27 and 28. The degree ofangulation or angular expansion is variable and incremental withincremental rotation of the driver 23 and the surgeon may advantageouslyselect the desired height of the anterior end of the spacer 10 accordingto patient anatomy by rotating the driver 23 only as much as is neededto expand and angulate the spacer 10 as desired by the surgeon. Therange of angulation of each endplate 14 is approximately between 0 and15 degrees from the horizontal. To collapse or readjust the spacer 10,the driver 23 can be rotated in the opposite direction to reduce theheight and angle of the spacer 10. If needed the driver 23 can thenagain be rotated to increase the height again and repeated as needed forsurgeon satisfaction. Variable and incremental rotation reduces theheight as needed. Both the upper and the lower endplates 14 are wedgedapart by the anterior actuator 16 and both of the upper and lowerendplates 14 move away from the longitudinal axis of the spacer 10uniformly at the anterior end for anterior angular expansion. The driver23 may be color coded with a color band around the driver 23 at alocation to denote the distance to insert the driver 23 for anteriorangular expansion. The driver 23 may also be marked with an arrow, aline or other indicia to denote the insertion limit for anterior angularexpansion.

Turning now to FIGS. 29-30, anterior angular expansion may also becombined with uniform parallel expansion in which the posterior drivescrew 22 is rotated to increase the height of the proximal end prior toor subsequent to anterior angular expansion in which the driver 23 ispositioned such that the distal drive portion 130 engages only with theposterior drive screw 22 as shown in FIGS. 31A-31B. Alternatively, thedriver 23 may be positioned as shown in FIGS. 17A-17B for uniformparallel expansion prior to or subsequent to being positioned foranterior angular expansion as shown in FIGS. 26A-26B. The combination ofanterior angular expansion with parallel expansion results in thedistal/anterior end having an overall greater height than theproximal/posterior end of the spacer 10 resulting in an expanded andangulated condition of expansion. In essence, customized as well asvariable uniform parallel and angular expansion is made possible bypositioning the driver 23 to rotate one or both of the anterior andposterior drive screws 20, 22 providing the greatest flexibility inangulation and expansion.

Turning now to FIGS. 31-33, posterior angular expansion of the spacer 10will now be described. The spacer 10 is inserted into the anatomicaldisc space while it is in an unexpanded, collapsed state. The unexpandedstate is illustrated in FIGS. 1-4, 22 and 24. While the spacer 10 is inan unexpanded, low profile configuration, the distal end of the driver23 is inserted into the drive bore 124 of the posterior drive screw 22and moved in a distal direction relative to the spacer 10 until,preferably, the entire length of the distal drive portion 130 isinserted into the drive bore 124 of the posterior drive screw 22. Acolor-coded marker or other indicia may be provided on the driver 23 toindicate to the user where to stop insertion of the driver 23 forposterior angular expansion. The driver 23 is not inserted all the wayuntil abutment with the neck portion 134 is achieved. Instead, insertionof the driver 23 is arrested when the distal drive portion 130 isengaged with the posterior drive screw 22, in particular, when thehexalobe-shaped, bore-engaging cross-section of the distal drive portion130 is engaged with the hexalobe-shaped, driver-engaging cross-sectionof the drive bore 124 of the posterior drive screw 22 as shown in FIGS.31A-31B. This partial insertion of the driver 23 leaves the anteriordrive screw 20 completely disengaged from the driver 23. As a result,when the driver 23 is rotated in one of a clockwise direction orcounterclockwise direction to bring the spacer 10 into an expandedstate, the posterior drive screw 22 will only be rotated and theanterior drive screw 22 will not be rotated When the driver 23 isrotated in this position, the posterior drive screw 22 moves in a distaldirection with respect to the housing 12 due to the right-handedness ofthe threads of the posterior drive screw 20. As the posterior drivescrew 22 moves distally, it moves the posterior actuator 18 distallyalong with it. The leading surfaces 90 of the upper and lower posterioractuator segments 116 will contact the posterior ramps 60 and slidealong the posterior ramps 60 to wedge the upper and lower endplates 14apart increasing the distance between the endplates 12 at the posteriorend bringing the posterior/distal end of the spacer 10 into an expandedangular condition. In posterior angular expansion, the posterior drivescrew 22 moves distally. Only the proximal end of the spacer 10 willincrease in height as both the upper and lower endplates 14 are wedgedapart uniformly oppositely from the longitudinal axis of the spacer 10;whereas, the anterior/distal end of the spacer 10 will remain in anunexpanded state creating an angle of the upper endplate 14 and lowerendplate 14 with respect to the horizontal housing 12. The spacer 10 ina condition of posterior angular expansion is shown in FIGS. 32 and 33.The degree of angulation or angular expansion is variable with rotationof the driver 23 and the surgeon may advantageously select the desiredheight of the posterior end of the spacer 10 according to patientanatomy by rotating the driver 23 only as much as is needed to expandand angulate the spacer 10 as desired by the surgeon. The range ofangulation of each endplate 14 is approximately between 0 and 15 degreesfrom the horizontal. To collapse or readjust the spacer 10, the driver23 can be rotated in the opposite direction to reduce the height andangle of the spacer 10. If needed the driver 23 can then again berotated to increase the height again and repeated as needed for surgeonsatisfaction. Variable rotation increases or reduces the height asneeded. Both the upper and the lower endplates 14 are wedged apart bythe posterior actuator 18 and both of the upper and lower endplates 14move away from the longitudinal axis of the spacer 10 uniformly at theposterior end for posterior angular expansion.

Turning now to FIGS. 34-35, posterior angular expansion may also becombined with uniform parallel expansion in which the anterior drivescrew 20 is rotated to increase the height of the distal end prior to orsubsequent to posterior angular expansion in which the driver 23 ispositioned such that the distal drive portion 130 engages only with theanterior drive screw 22 as shown in FIGS. 26A-26B. Alternatively, thedriver 23 may be positioned as shown in FIGS. 17A-17B for uniformparallel expansion prior to or subsequent to being positioned forposterior angular expansion as shown in FIGS. 31A-31B. The combinationof posterior angular expansion with parallel expansion results in theproximal/posterior end having an overall greater height than thedistal/anterior end of the spacer 10 resulting in an expanded andangulated condition of expansion. In essence, customized as well asvariable uniform parallel and angular expansion is made possible bypositioning the driver 23 to rotate one or both of the anterior andposterior drive screw 20, 22 providing the greatest flexibility inangulation and expansion. Each of the posterior and anterior ends may beexpanded and/or angled independently to a height or angle as desiredwith incremental rotation in either direction to increase or decreasethe angle and/or height with the use of one driver that is positionedvariably along the longitudinal axis to effect the different states ofexpansion/angulation.

The expandable interbody spacer 10 is made of any suitable biocompatiblematerial. The expandable interbody spacer 10 may be made from any one orcombination of one or more metal such as titanium, ceramic, polymer suchas polyether ether ketone (PEEK), carbon fiber reinforced polymer,biomaterial including but not limited to any of a number ofbiocompatible implantable polymers including PEKK, PEKEK,polyetheretherketone (PEEK) being preferred, titanium ceramic, bone orother material etc. The present invention can be employed and issuitable for use anywhere along the spine including but not limited tocervical, thoracic, lumbar or sacral or between other bony structuresoutside of the spinal region. Embodiments of the present invention arestandalone interbody devices which may be designed in the general styleof a TLIF device, PLIF device, ALIF or other device. In addition, thesize and/or shape of the basic embodiments disclosed herein may beadapted by one skilled in the art for use in various levels of thespine, namely the cervical spine, thoracic spine and the lumbar spine.Thus, while various embodiments herein may be described by way ofexample with respect to the lumbar spine such disclosures apply withequal weight to the other levels of the spine.

It is understood that various modifications may be made to theembodiments of the interbody spacer disclosed herein. Therefore, theabove description should not be construed as limiting, but merely asexemplifications of preferred embodiments. Those skilled in the art willenvision other modifications within the scope and spirit of the presentdisclosure.

We claim:
 1. An expandable interbody spacer having a longitudinal axis,a proximal end and a distal end, comprising: a housing having two sidesinterconnected by a distal endwall and a proximal endwall defining ahollow interior; the distal endwall having a threaded distal opening andthe proximal endwall having a threaded proximal opening; an upperendplate and a lower endplate each having a posterior end and ananterior end, a bone-engaging surface and an interior surface oppositeto the bone-engaging surface; the interior surface of each of the upperand lower endplates having an anterior ramp surface extending at anangle with respect to the interior surface and a posterior ramp surfaceextending at an angle with respect to the interior surface; an anterioractuator located between the interior surfaces of the upper endplate andthe lower endplate near the distal end of the spacer; the anterioractuator comprising an upper anterior actuator segment and a loweranterior actuator segment; the upper anterior actuator segment having acurved inner surface and an angled leading surface for contact with theanterior ramp surface of the upper endplate; the lower anterior actuatorsegment having a curved inner surface and an angled leading surface forcontact with the anterior ramp surface of the lower endplate; aposterior actuator located between the interior surfaces of the upperendplate and the lower endplate near the proximal end of the spacer; theposterior actuator comprising an upper posterior actuator segment and alower posterior actuator segment; the upper posterior actuator segmenthaving a curved inner surface and an angled leading surface for contactwith the posterior ramp surface of the upper endplate; the lowerposterior actuator segment having a curved inner surface and an angledleading surface for contact with the posterior ramp surface of the lowerendplate; an anterior drive screw comprising a proximal ball headconnected to a distal threaded shank; the proximal ball head of theanterior drive screw being located between the curved inner surfaces ofthe upper and lower anterior actuator segments; the distal threadedshank being threadingly connected to the threaded distal opening; theanterior drive screw having an anterior drive bore extending from aproximal opening along a longitudinal drive axis; and a posterior drivescrew comprising a proximal threaded shank connected to a distal ballhead; the distal ball head of the posterior drive screw being locatedbetween the curved inner surfaces of the upper and lower posterioractuator segments; the proximal threaded shank being threadinglyconnected to the threaded proximal opening; the posterior drive screwhaving a posterior drive bore extending along the longitudinal driveaxis between a proximal opening in the threaded shank and a distalopening in the distal ball head; wherein rotation of the posterior drivescrew in a first direction relative to the proximal end of the spaceraround the longitudinal drive axis translates the posterior drive screwdistally to wedge apart and expand the distance between the posteriorends of the upper and lower endplates; wherein rotation of the anteriordrive screw in the first direction relative to the proximal end of thespacer around the longitudinal drive axis translates the anterior drivescrew proximally to wedge apart and expand the distance between theanterior ends of the upper and lower endplates; wherein rotation of theposterior drive screw in a second direction relative to the proximal endof the spacer around the longitudinal drive axis translates theposterior drive screw proximally to reduce the distance between theposterior ends of the upper and lower endplates; and wherein rotation ofthe anterior drive screw in the second direction relative to theproximal end of the spacer around the longitudinal drive axis translatesthe anterior drive screw distally to reduce the distance between theanterior ends of the upper and lower endplates.
 2. The expandableinterbody spacer of claim 1 wherein the posterior and anterior drivescrews are simultaneously and independently rotatable.
 3. The expandableinterbody spacer of claim 1 wherein the posterior and anterior drivescrews are simultaneously and independently rotatable from the proximalend of the spacer.
 4. The expandable interbody spacer of claim 1 whereinthe proximal threaded shank of the posterior drive screw has threadsopposite in direction from threads of the distal threaded shank of theanterior drive screw.
 5. The expandable interbody spacer of claim 1wherein the upper and lower anterior actuator segments snap around theproximal ball head of the anterior drive screw to capture the proximalball head between the curved inner surfaces such that the anterior drivescrew is rotatable relative to the anterior actuator; and wherein theupper and lower posterior actuator segments snap around the distal ballhead of the posterior drive screw to capture the distal ball headbetween the curved inner surfaces such that the posterior drive screw isrotatable relative to the posterior actuator.
 6. The expandableinterbody spacer of claim 1 wherein the proximal ball head of theanterior drive screw is spherical in shape and the inner surfaces of theupper and lower anterior actuator segments together define acorresponding spherical shape; and wherein the distal ball head of theposterior drive screw is spherical in shape and the inner surfaces ofthe upper and lower posterior actuator segments together define acorresponding spherical shape.
 7. The expandable interbody spacer ofclaim 1 wherein each of the upper and lower endplates includes first andsecond side rails extending from the interior surface; and wherein theanterior and posterior ramp surfaces of each of the upper and lowerendplates are formed between the first and second side rails.
 8. Theexpandable interbody spacer of claim 1 wherein the longitudinal driveaxis is coaxial with the longitudinal axis of the spacer.
 9. Theexpandable interbody spacer of claim 1 wherein the leading surfaces ofthe upper and lower anterior actuator segments face toward the proximalend and the leading surfaces of the upper and lower posterior actuatorsegments face toward the distal end.
 10. The expandable interbody spacerof claim 1 wherein the leading surfaces of the upper and lower anterioractuator segments are angled away from each other toward the distal endof the spacer and the leading surfaces of the upper and lower posterioractuator segments are angled away from each other toward the proximalend of the spacer.
 11. The expandable interbody spacer of claim 1wherein the first direction is clockwise relative to the proximal end ofthe spacer, and wherein the second direction is counterclockwiserelative to the proximal end of the spacer.
 12. A driver for anexpandable interbody spacer having a proximal end and a distal end,comprising: a first drive portion having a first length extending alonga longitudinal axis of the driver; the first drive portion having afirst diameter and a non-circular cross-sectional first shape takenperpendicular to the longitudinal axis extending along the first length;a second drive portion having a second length extending along thelongitudinal axis; the second drive portion having a second diameter anda non-circular cross-sectional second shape taken perpendicular to thelongitudinal axis extending along the second length; a middle portionlocated between the first drive portion and the second drive portion;the middle portion having a middle length extending along thelongitudinal axis; the middle portion having a middle diameter and across-sectional middle shape taken perpendicular to the longitudinalaxis extending along the middle length; a handle located at the proximalend; the handle having a handle length extending along the longitudinalaxis and a handle diameter; wherein the first drive portion extends fromthe distal end of the driver and is connected to a distal end of themiddle portion; the middle portion extends from a proximal end of thefirst drive portion and is connected to a distal end of the second driveportion; and the handle extends from a proximal end of the second driveportion to the proximal end of the driver.
 13. The driver of claim 12wherein the first diameter and the second diameter are each a majordiameter, and wherein the first and second drive portions each furthercomprise a minor diameter; each respective major diameter being largerthan each respective minor diameter.
 14. The driver of claim 12 whereinthe first diameter and the second diameter are equal.
 15. The driver ofclaim 12 wherein the first diameter and the second diameter are largerthan the middle diameter.
 16. The driver of claim 12 wherein the handlediameter is larger than both the first diameter and the second diameter;and both the first diameter and the second diameter are larger than themiddle diameter.
 17. The driver of claim 16 wherein the first diameterand the second diameter are the same.
 18. The driver of claim 12 whereinthe handle includes a neck portion located proximal to the second driveportion; the neck portion having a diameter smaller than the handlediameter and larger than the second diameter.
 19. The driver of claim 12wherein the first diameter is constant along the entire first length;the second diameter is constant along the entire second length; thefirst shape is constant along the entire first length; and the secondshape is constant along the entire second length.
 20. The driver ofclaim 12 wherein the first shape and the second shape are the sameshape.
 21. The driver of claim 12 wherein the middle shape is circular.22. The driver of claim 12 wherein the middle diameter is the same asthe first diameter and the second diameter, and wherein the middle shapeis circular.
 23. The driver of claim 12 wherein the second length isshorter than the first length.
 24. A method comprising: providing anexpandable interbody spacer having a longitudinal axis, a proximal endand a distal end; the spacer including: a housing having a threadedproximal opening and a threaded distal opening; an upper endplate havingan anterior end and a posterior end, an anterior angled surface and aposterior angled surface; a lower endplate having an anterior end and aposterior end, an anterior angled surface and a posterior angledsurface; an anterior drive screw threadingly connected to the distalopening; the anterior drive screw having an anterior ball head connectedto a threaded anterior shaft and an anterior drive bore having a borediameter and a cross-sectional shape taken perpendicular to andextending along a longitudinal drive axis; an anterior actuator coupledto the anterior drive screw; the anterior actuator having an upper drivesurface for mating with the anterior angled surface of the upperendplate and a lower drive surface for mating with the anterior angledsurface of the lower endplate; a posterior drive screw threadinglyconnected to the proximal opening; the posterior drive screw having aposterior ball head connected to a threaded posterior shaft and aposterior drive bore having a bore diameter and cross-sectional shapetaken perpendicular to and extending along the longitudinal drive axis;the posterior drive bore being coaxially aligned with the anterior drivebore along the longitudinal drive axis; a posterior actuator coupled tothe posterior drive screw; the posterior actuator having an upper drivesurface for mating with the posterior angled surface of the upperendplate and a lower drive surface for mating with the posterior angledsurface of the lower endplate; providing a driver having a longitudinalaxis, a proximal end and a distal end; the driver including: a firstdrive portion having a first length extending along a longitudinal axisof the driver; the first drive portion having a first diameter and anon-circular cross-sectional first shape taken perpendicular to thelongitudinal axis extending along the first length; the first shapebeing sized and configured to matingly engage the anterior drive boreand the posterior drive bore; a second drive portion having a secondlength extending along the longitudinal axis; the second drive portionhaving a second diameter and a non-circular cross-sectional second shapetaken perpendicular to the longitudinal axis extending along the secondlength; the second shape being sized and configured to matingly engagethe posterior drive bore; a middle portion located between the firstdrive portion and the second drive portion; the middle portion having amiddle length extending along the longitudinal axis; the middle portionhaving a middle diameter and a cross-sectional middle shape takenperpendicular to the longitudinal axis extending along the middlelength; a handle located at the proximal end; the handle having a handlelength extending along the longitudinal axis and a handle diameter;wherein the first drive portion extends from the distal end of thedriver to a distal end of the middle portion; the middle portion extendsfrom a proximal end of the first drive portion to a distal end of thesecond drive portion; and the handle extends from a proximal end of thesecond drive portion to the proximal end of the driver.
 25. The methodof claim 24 further including the steps of: inserting the driver intothe anterior drive bore and the posterior drive bore from the proximalend of the spacer such that the first drive portion of the driver islocated inside the anterior drive bore and the second drive portion ofthe driver is located inside the posterior drive bore; and rotating thedriver in a clockwise direction relative to the proximal end of thespacer to simultaneously and uniformly expand apart the anterior endsand the posterior ends of the upper and lower endplates.
 26. The methodof claim 25 further including the step of rotating the driver in acounterclockwise direction relative to the proximal end of the spacer tosimultaneously and uniformly move the anterior ends and the posteriorends of the upper and lower endplates toward each other to reduce thedistance between the upper and lower endplates.
 27. The method of claim24 further including the steps of: inserting the driver into theanterior drive bore and the posterior drive bore from the proximal endof the spacer such that the first drive portion of the driver is locatedinside the anterior drive bore and the second drive portion of thedriver is located proximal to the posterior drive screw and outside theposterior drive bore; and rotating the driver in a clockwise directionrelative to the proximal end of the spacer to simultaneously angulatethe upper and lower endplates such that the distance between the upperand lower endplates at the distal end of the spacer increases withclockwise rotation relative to the upper and lower endplates at theproximal end of the spacer.
 28. The method of claim 27 further includingthe step of rotating the driver in a counterclockwise direction relativeto the proximal end of the spacer to simultaneously and uniformly movethe anterior ends of the upper and lower endplates toward each other toreduce the distance between the upper and lower endplates at the distalend of the spacer without changing the distance between the posteriorends of the upper and lower endplates.
 29. The method of claim 24further including the steps of: inserting the driver into the posteriordrive bore from the proximal end of the spacer such that the first driveportion of the driver is located inside the posterior drive screw andthe second drive portion of the driver is proximal to the posteriordrive screw and outside of the spacer; and rotating the driver in aclockwise direction relative to the proximal end of the spacer tosimultaneously angulate the upper and lower endplates such that thedistance between the upper and lower endplates at the proximal end ofthe spacer increases with clockwise rotation relative to the upper andlower endplates at the distal end of the spacer.
 30. The method of claim29 further including the step of rotating the driver in acounterclockwise direction relative to the proximal end of the spacer tosimultaneously and uniformly move the posterior ends of the upper andlower endplates toward each other to reduce the distance between theupper and lower endplates at the proximal end without changing thedistance between the posterior ends of the upper and lower endplates.31. The method of claim 24 wherein the first length of the driver isequal to the length of the anterior drive screw, and the second lengthof the driver is shorter than the posterior drive screw.
 32. The methodof claim 24 wherein the spacer has a length equal to the sum of thefirst portion, the second portion and the middle portion.
 33. The methodof claim 24 wherein the middle diameter of the driver is smaller thanthe bore diameter of the posterior drive screw.
 34. The method of claim24 wherein the middle portion of the driver is configured not tomatingly engage with the posterior drive screw.